SLC31A1 and cholangiocarcinoma: The combination of two single polymorphisms, c.354T>C (p.Asn118Asn, rs11615) in ERCC1, a DNA repair gene, and c.136-14361C>A (g.113241753C>A, rs12686377) in SLC31A1, encoding CTR1, one of the main transporters of platinum derivatives, has been proposed as a potential biomarker to predict the response to the combined treatment of gemcitabine with cisplatin, which is the first-line chemotherapeutic regimen for CCA patients [133].